In recent years, as environmentally friendly vehicles, hybrid vehicles are receiving broad attention. In a hybrid vehicle, in addition to a conventional engine, a power storage device (battery), an inverter, and an electric motor (motor) driven by the inverter serve as a motive power source.
In such a vehicle, if an engine is regularly started but driving time is short, fuel in a fuel tank may be hardly consumed for a long time. In this case, degradation and alteration of fuel may result in deteriorated starting capability of engine and deteriorated emission characteristics.
Japanese Patent Laying-Open No. 2005-226462 discloses a fuel supplying apparatus in which a fuel pump and a path switching means are provided integrally. This fuel supplying apparatus is configured to be switchable between an operating state in which fuel in a fuel tank is supplied to a carburetor and a circulation state in which fuel in the carburetor is returned to the fuel tank. Where the engine is stopped for a long time, the fuel supplying apparatus can be operated to be in the circulation state, to eliminate inconveniences, such as a failure in starting, due to degradation and alteration of fuel for the next engine start.
There is proposed a hybrid vehicle capable of traveling a longer distance using only an output of a motor by charging a direct current electric power supply by means of an external electric power supply. When a user drives such a hybrid vehicle only for a short distance, the engine is more unlikely to operate. If such short distance traveling of the hybrid vehicle is repeated, the engine may be stopped for a long time.
When the stop period of the engine is long, for example, moisture separated from fuel remaining in a pipe may cause rusting in the pipe. Further, progress in degradation of the fuel in the pipe may have an influence over the operation of the engine.
To prevent such a problem, the method disclosed in Japanese Patent Laying-Open No. 2005-226462, i.e., the method for returning all the fuel in the pipe to the fuel tank is conceived. However, according to this method, when the traveling mode of the hybrid vehicle is set at a mode that permits operation of the engine, fuel cannot be supplied to the engine immediately because no fuel is left in the pipe. Accordingly, the engine cannot be started immediately, which may influence the traveling of the hybrid vehicle.